721764 has 48 divisors (see below), whose sum is σ = 1928640. Its totient is φ = 233280.

The previous prime is 721739. The next prime is 721783. The reversal of 721764 is 467127.

721764 = T₁ + T₂ + ... + T₁₆₂.

721764 is a nontrivial binomial coefficient, being equal to C(164, 3).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

721764 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is the 162-nd tetrahedral number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4347 + ... + 4509.

It is an arithmetic number, because the mean of its divisors is an integer number (40180).

2⁷²¹⁷⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (964320).

721764 is an abundant number, since it is smaller than the sum of its proper divisors (1206876).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721764 is a wasteful number, since it uses less digits than its factorization.

721764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 209 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 721764 is about 849.5669485097. The cubic root of 721764 is about 89.7012315129.

It can be divided in two parts, 721 and 764, that added together give a triangular number (1485 = T₅₄).

The spelling of 721764 in words is "seven hundred twenty-one thousand, seven hundred sixty-four".